Also present within normal anterior pituitary gland, so the presence of pituitary adenoma must be confirmed on H&E stains (occasionally with the support of ancillary stains such as reticulin for normal adenohypophyseal architecture)

A 57 year old man presents with bitemporal hemianopsia, mildly elevated serum prolactin and MRI showing a 2.5 cm mass within the sella turcica, which is noted to extend upward and push on the optic chiasm. Physical examination reveals no signs of hormone excess (no evidence of gynecomastia, galactorrhea, Cushing syndrome, acromegaly, etc.) and formal visual field testing confirms decreased vision in the outer half of the visual fields. Transsphenoidal resection confirms pituitary adenoma by routine stains. The adenoma shows the following immunoreactivity: SF1+, Pit1- and ACTH-. How is this adenoma best classified?

Corticotroph adenoma

Gonadotroph adenoma

Null cell adenoma

Prolactinoma

Board review answer #1

B. Gonadotroph adenoma. Absence of signs of hormone excess is the usual finding in gonadotroph adenoma. A small rise in prolactin can be seen in association with any lesion of the sella turcica that impinges on the stalk of the pituitary, interrupting dopaminergic inhibition of lactotrophs in the nonneoplastic anterior pituitary gland. SF1 immunohistochemistry is the most sensitive and specific means of classifying gonadotroph adenoma.

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